No, but if you ask me, you're best bet at learning how to draw manga is learning how to draw, period. My favorite artists show an impeccable respect to human anatomy, so doing some figure drawing would do wonders for your ability.
Definitely this
If you're in school take drawing classes
Most of all: Draw. Draw all the time. Draw in your sleep. Draw in shower. Draw when you're in a gun fight (and I mean with a pencil though you might get killed)
Draw anything and everything
Spheres, cones, cubes, and cylinders make for excellent starting points. Curtains are a little bit tougher but once you get shadows, cast shadows, and drop shadows down it should be a bit easier
I would also recommend getting charcoal to draw with. It's really easy to use though it does make a bit of a mess.
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I need to read more Fairy Tail
It's so cool! I wanna get more Rave Master too! But I really like Fairy Tail better